The Original Vampires of The Vampire Diaries were born witches, but their transition to becoming vampires may not have ruled out their potential to also have been witch-vampire hybrids. The ritual that the Mikaelsons' mother, Esther, performed granted her children the opportunity to become vampires at the price of being not only disconnected from Nature but also from the Ancestors as witches. The inability to practice magic by channeling either of these two sources of power rendered the Original Vampires presumably incapable of practicing any magic.
However, it was neither confirmed nor denied that all forms of magic were entirely unavailable for the other Mikaelson family members aside from Klaus to practice after their transition. While Nature may have inherently revoked the Mikaelsons' ability to use magic because of their unnatural status as vampires, the Ancestors permitted their creation just as they permitted Qetsiyah to create the Other Side and the first immortals, Silas and Amara. Silas was a psychic-witch who, after becoming immortal–an unnatural being in the eyes of Nature–was still able to practice magic, albeit dark magic known as Expression. It is a type of magic that could neither be granted nor taken away by Nature nor the Ancestors. Therefore, theoretically, it's reasonable to think the Original Vampires could have practiced the same type of Expression magic as Silas.
Why Silas Was Technically A Vampire Diaries Hybrid
The hybrid status could also be extended to Silas, one of five doppelgängers in The Vampire Diaries. He once acerbically explained to Elizabeth Forbes, "I came first. Vampires are nothing more than a disgusting perversion of me. I'm unkillable, I'm immortal, and I'm psychic; and to function, I need human blood, but don't ever call me a vampire." Technically, that is fair to say as Silas lacked the other supernatural vampire perks, though his powers of illusion never made it seem that way. Being a blood-sucking immortal being, nonetheless, is still a dual status attached to his original witch heritage.
How The Original Vampires Differ From Silas
The roots of Esther's vampire spell were found in Qetsiyah's immortality spell. The only key difference is that Silas was not required to have died or engage in Vampire Diaries blood sharing to obtain immortality. Perhaps the Ancestors learned their lesson from Silas and Qetsiyah's ordeal when they permitted the creation of vampires by Esther. In an attempt to maintain balance and prevent beings that were too powerful from coming into existence, a price had to be paid: an old life for a new life; or, witch status for vampire status. Thus, this price of death to transition was possibly also the death of the Original Vampires' previous living status as witches to become undead immortal vampires. This, however, resulted in the unforeseen creation of the werewolf-vampire hybrid, Klaus, an unintended loophole in Esther's spell.
If the death and transition indeed removed the Original Vampires' witch statuses as per Vampire Diaries' witch rule, then they are not hybrids, save for Klaus. Still, it is possible that their status as witches was not entirely removed, but rather suppressed by Nature and the Ancestors. If that is the case, then it is possible that, like Silas who was cut off from Nature, The Vampire Diaries’ Original Vampires could have practiced the same dark magic that allowed Silas to continue practicing magic. Technically, the vampire-witch hybrid status of the Original Vampires may have simply been untapped.